why chiefs linebacker jovan belcher shot and killed his girlfriend, the mother of his baby girl, then drove to arrowhead stadium and killed himself in front of his coach and general manager. and belcher's uniform hung untouched in his locker. members of the chiefs organization struggled for answers. >> it's tough. i miss him, you know. he's a great guy. a great teammate. >> he was an individual that did something that he snapped, and that, i don't understand. i probably never will. >> no history of concussions from belcher either. his teammates and 62,000 fans observed a moment of silence for victims of domestic violence. we're going to have highlights from the game in just a moment. >>> and new research is coming to light strengthening the link between long-term brain damage and playing football. espn and pbs' front line are working on a documentary. and they report that scientists have discovered 28 new cases of chronic brain disease in football players who have died, 15 of them former nfl players. one researcher says the sheer volume of cases will overwhelm anybody who wants to den